The present invention relates to a chip-type semiconductor light emitting device in which a light emitting element chip is bonded on an insulation substrate, and light is applied in a direction parallel to the surface of the insulation substrate, namely, in a direction of a side surface of the device. More particularly, the invention relates to a chip-type light emitting semiconductor light emitting device which emits from a side surface, and is capable of widening a directivity so that a portion which is referred to as a dark decreases where light is not allowed to be incident on a light transmitting plate even with the widening of a interval of the light emitting devices even in the case where light source is adopted which allows light to be incident on a light transmitting plate which serves, for example, as a backlight of a liquid crystal display device.
A chip-type semiconductor light emitting device which is generally used is constituted in such a manner that light is emitted toward an upper surface side by bonding a light emitting element(diode) chip(hereinafter referred to as an LED chip) on an insulation substrate and covering on the periphery of the LED chip with a light transmitting resin. However, since it is required to install a light source on a side of a plate-like light transmitting plate, for example, as a light source for allowing light to be incident on the light transmitting plate of the backlight of the liquid crystal display device, a lamp-type light emitting device is conventionally used. However, these days, a so-called side surface emitting chip-type light emitting device(chip-type light emitting device which emits from the side face) is used in which the chip-type light emitting device is allowed to emit light in a direction parallel to the insulation substrate. Such side surface emitting chip-type light emitting device has a structure, for example, as shown in FIG. 4.
In FIG. 4, reference numeral 21 denotes an insulation substrate formed of, for example, a glass epoxy or the like. On the sides of both end portions of the insulation substrate 21, conductive films are provided, and a pair of electrodes 22 and 23 are formed thereon. On the surface of the insulation substrate, an LED chip 24 is bonded and is electrically connected to the pair of the electrodes 22 and 23 by wire 25 or the like (in an example shown in FIG. 4, one of the electrodes of the LED chip 24 is formed on the rear surface side thereof and is directly connected to the electrode 22 with the bonding paste). Furthermore, the periphery thereof is covered with a light transmitting resin 26. Furthermore, the external circumference of the resin 26 is covered with a case 27 formed of a light shielding material having a light reflecting characteristic. Incidentally, the chip-type semiconductor light emitting device has a structure constituted in such a manner that a through holes 21a are provided on both end portions of the insulation substrate 21, the electrodes 22 and 23 are connected to the rear surface of the substrate 21 with a conductive films provided inside of the through holes 21a, and printed substrate, mother board or the like to be electrically connected.
In the case where such light emitting device is installed on the side surface of the light transmitting plate to constitute a backlight, as shown in FIG. 5, the chip-type light emitting device has a structure constituted in such a manner that a side surface emitting chip-type light emitting device 20 is arranged on one side wall of the light transmitting plate 30 in a definite interval, light is allowed to be incident on the inside of the light transmitting plate 30 and is allowed to be scattered within the light transmitting plate 30 to allow light to be applied from the surface the light transmitting plate 30.
As described above, the conventional side surface emitting chip-type light emitting device is formed in such a manner that a light transmitting resin is allowed to be exposed only on one side surface of the insulation substrate having a rectangular shape so that light is allowed to be applied in a direction parallel to the substrate from one side surface of the insulation substrate. Then, the surfaces other than the one side surface is formed in such a manner that the light transmitting resin is completely covered with the case 27 to allow light to be applied only from the side of the one side surface with the result that the emitted light is effectively used and the efficiency of the light emitted to outside can be improved. Consequently, the chip-type light emitting device has a structure such that the exposed portion of the light transmitting resin and the bottom portion on the opposite side thereof has a concave shape in the case, and an LED chip is placed on the bottom portion side with the result that light is applied from an open portion of the case 27.
As a consequence, a bundle of light that is radiated from one side surface is such that a strong light is emitted in a central direction and the directivity thereof is narrowed down. As a consequence, as shown in FIG. 5, when light emitting devices are arranged in a definite interval on a side surface of the light transmitting plate 30, a portion which is referred to as a dark portion 31 is generated in which light is not allowed to be incident at a portion of the light transmitting plate 30 between the light emitting devices 20. A portion of such dark portion 31 is compensated with light which is reflected and brought back within the light transmitting plate 30, but the dark portion 31 has a problem such that the portion has a different luminance from a portion on which light is directly allowed to be incident so that the luminance does not become uniform on the entire surface of the light transmitting plate 30.
In order to solve such a problem, the interval between the light emitting devices must be narrowed down with an increase in the number of the light emitting devices with the result that the production cost will increase.
The present invention has been made to solve such a problem, and an object of the invention is to provide a side surface emitting chip-type semiconductor light emitting device having a wide directivity wherein a dark is hardly generated between light sources in the case where the light sources for use in backlights are arranged in a definite interval.
Another object of the present invention is to provide a side surface emitting chip-type semiconductor light emitting device which can be manufactured at simple steps wherein bending of wires is not generated at the manufacturing stage so that a good quality light emitting device can be provided.
The chip-type semiconductor device according to the present invention comprises:
a rectangle-shaped insulation substrate on which a pair of electrodes are provided;
a light emitting element chip provided on the insulation substrate, the device having an n-side electrode and a p-side electrode connected to the pair of electrodes respectively;
a light transmitting member being provided on the insulation substrate and covering the periphery of the light emitting element chip; and
a light reflection member covering at least a part of the light transmitting member, the light reflection member being provided to radiate light from the portion of the light transmitting member which is not covered and exposed;
wherein the above light reflection member is formed in such a manner that the portion of the light transmitting member which is not covered with the light reflection member and is exposed is exposed over from one side in the rectangle shape to at least a part of the side portions on both sides which continue to the one side.
Here, the light transmitting member refers to a material which transmits light which is emitted with the light emitting element chip. The material is not required to be transparent. A material which transmits light while scattering light such as white milk light or the like is included in the material.
With the constitution of such a structure, light is applied not only from one side surface but from the other side surface which continues to the one side surface with the result that the directivity is extremely widened, and the dark portion is largely decreased even when the device is used in the backlight or the like. As a consequence, a backlight with a uniform luminance can be obtained with small light source.
Out of the n-side and the p-side electrodes in the light emitting element chip, at least one of the electrodes is connected to one of the pair of the electrodes with wire bonding. When the wire is bonded in such a manner that a direction in which a wire in the wire bonding is extended is approximately parallel to one side which light transmitting member is exposed on, preferably the wire is not allowed to flow or to be severed with the flow of resin in the case where this semiconductor light emitting device is manufactured. In other words, in the case where the light emitting device of this kind is manufactured, for example, about 1000 LED chips are arranged and bonded both vertically and horizontally on a large insulation substrate. Then, in order to form the light transmitting member having the above structure, it is preferable to manufacture the device from the viewpoint of a reduction in the manufacture cost, by flowing the resin from one end portion of a group of devices which are arranged horizontally, for example, as shown in FIG. 2(b). Since the direction of the above wire corresponds to the direction in which this resin flows, a resistance with the resin becomes small and the wire flow and the wire disconnection are hardly generated.
Preferably, a boundary portion between one side and side portions on both sides which continue to the side is formed in an arc-like shape in a plane shape because the continuity of light which is applied from one side surface to the side of the adjacent side surface is improved and the directivity is improved.
When the above light transmitting member is made of a material having a light scattering function, the directivity is widened in the same manner. In this case, the above boundary portion is not formed in an arc-like shape and may be formed in a square shape. In the case of the formation of the portion in the square shape, since the flow of the resin can be made smooth with a simple die structure, a void or the like is not formed in the light transmitting member and the light radiation characteristic is improved.
When a pair of rear electrodes are formed on the rear side of the above insulation substrate, the above pair of rear electrodes are electrically connected to the pair of electrodes provided on the surface of the above insulation substrate via the through hole, and at the same time, the surface side of the through hole is sealed respectively with the above pair of the electrodes provided on the surface of the insulation substrate, the through hole is sealed even in the case where the light transmitting member is formed with molding formation with the result that the molding formation can be done without the dripping of the resin.
When the above reflection member is formed in such a manner that the member is bent to a back side from an upper surface, and a section form is an L-shape, the reflection member which is formed in advance in a length corresponding to the number of the members arranged horizontally is covered, and then, the resin of the light transmitting member can be flowed from the side with the result that the light emitting device can be simply manufactured without the formation of a void such as air reservoir or the like within the light transmitting member.
When the back side wall of the above reflection member which is the side wall opposite to the one side of the exposed light transmitting member is formed in a concave shape, light is collected forward to some extent. Thus, the emitted light can be effectively used.